#### Answer

75 feet

#### Work Step by Step

Because the tower forms a 90-degree angle, we use the Pythagorean Theorem, $a^{2}+b^{2}=c^{2}$.
We are given the length of two sides, $a$ and $b$. $a=45$ feet and $b=60$ feet.
$45^{2}+60^{2}=c^{2}$
Now we must solve for $c^{2}$.
Evaluate the exponents: $2025+3600=5625$
$5625=c^{2}$
Solve for $c^{2}$.
$\sqrt 5625 =75$
$75^{2}=5625$
$45^{2}+60^{2}=75^{2}$
Because $c=75$, the length of the cable is $75$ ft.